Tree Twig Anatomy: Ecosystem Stress, Growth Rates, Winter Identification

Summary: Professor Kim D. Coder of Athens, Georgia, uses tree twig anatomy to research tree-related ecosystem stress, growth rates and winter identification.

Tree twig anatomy conveys details of ecosystem stress and growth rates and also provides plant identification in winter; autumn olive (Elaeagnus umbellata) twigs with thorns and leaves in spring: James H. Miller/USDA Forestry Service/Bugwood.org, CC BY 3.0 United States, via Forestry Images

Advanced Twig Anatomy: Starting Little to Get Big (Part I) addresses tree twig anatomy for indicating ecosystem stress and species growth rates and winter identification in the February 2014 Arborist News issue.

Kim D. Coder of North America's University of Georgia in Athens, Georgia, bases his discussion upon extensive experience with temperate deciduous angiosperms, also known as hardwoods. Focus and space call for excluding from discussion evergreen and persistent-leaved angiosperms and gymnosperms whose twigs confirm non-deciduous, species-specific ecosystem stress, growth rates and winter identifications. All twigs, whether angiosperm or gymnosperm, whether deciduous evergreen or persistent-leaved, deserve descriptions as "the current or most recent growth extension at the tips of branches."

Growing points emerge either "just behind and to the side" of, or within "protective bud scales" at, the tips of deciduous, evergreen and persistent-leaved tree twigs.

Twigs fit into tree twig anatomy as the first year's growth increments atop the second and the third year's branchlet attachments to the fourth year's branches. They generate growth, species and stress information by surviving cladoptosis, a tree "compartmentalization process" that naturally self-prunes and yearly sheds over 30,000 branches, branchlets and twigs.

Each twig section has to have only one each of bud-, flower- or leaf-generating nodal torus rings; growth-friendly internodes; leaves; petioles; and side or terminal buds. They include coppice shoots at stem base "suppressed growing points," crown-based long shoots with "normally elongated internodes" and root shoots with root base "adventitious growing points."

Crown-growing determinant short shoots with functional terminal growing points, indeterminant short shoots without and flower-, fruit-, leaf-generating, slow-growing, spine-tipped spur shoots join to narrow winter identification.

Tree twig anatomy keeps internodes species-specific in 1.9-millimeter (0.075-inch) slender, 4-millimeter (0.158-inch) moderately slender, 5-millimeter (0.197-inch) moderately stout or 5-plus-millimeter (0.197-plus-inch) robust or stout maximum diameters.

Cross-sectional shapes look angled, round or star-shaped for pith, the twig's primary-, soft-celled longitudinal center axis, and angular, fluted or ridged, oval or round for internodes. Pith manages chambered and multi-cross-walled, diaphragmed and thin cross-walled, excavated and hollow, solid or spongily perforated longitudinal views in declining, downward-hanging, downward-tending, drooping or upright twigs. It needs an encircling, medullary, non-ray cell-breached sheath surrounded by wood's "structural and vascular tissue" to protect chlorophyll-filled, first-year, live green pith cells from ecosystem stress.

Axil-derived, vascular tissue-filled spinescent thorn-like short spurs and spiniferous thorns or prickly epidermis- and periderm-anchored bristles and fruit-, leaf-, stipule stem-modified nodal thorns offer exterior armature.

Secondary growth, called girth expansion, pushes peridermal, secondary tissue generated by lateral meristems called phellogens crushingly against primary, simple-celled cortex supporting the bark's epidermal primary tissue. Girth quickens old phelloderm and phloem tissues intermingling as secondary cortex under corky periderm's even, mottled or striated smoothness, peeling papery-ness or furrowed, scaly, warty roughness.

Low-density, thin-walled peridermal lenticels distinctly, invisibly or visibly raised, sunken or surfacing atop epidermal gas exchange ports called stomates reveal rounding or horizontal- or longitudinal-elongated ovality. Trichomes, be they bristly, coarse, dense, flat-scaled, long, minute, silky, soft, sparse, star-shaped, stiff or straight, surface alongside lenticels on hairily pubescent, not hairlessly glabrous, twigs.

Tree twig anatomy always tells on species-specific, stress-induced characteristics, even on blue-gray caesious, blue-white glaucous, frosted-like pruinose, light-colored bloom, stickily glutinous or thickly viscid wax-coated epidermises.

Tree twigs serve as tree identifiers in winter; red maple (Acer rubrum) twig: Rob Routledge/Sault College/Bugwood.org, CC BY 3.0 United States, via Forestry Images

Acknowledgment

My special thanks to:
talented artists and photographers/concerned organizations who make their fine images available on the internet;
University of Illinois at Urbana-Champaign for superior on-campus and on-line resources.

Image credits:

autumn olive (Elaeagnus umbellata) twigs with thorns and leaves in spring: James H. Miller/USDA Forestry Service/Bugwood.org, CC BY 3.0 United States, via Forestry Images @ http://www.forestryimages.org/browse/detail.cfm?imgnum=0016044

Tree twigs serve as tree identifiers in winter; red maple (Acer rubrum) twig: Rob Routledge/Sault College/Bugwood.org, CC BY 3.0 United States, via Forestry Images @ http://www.forestryimages.org/browse/detail.cfm?imgnum=5488134

For further information:

Coder, Kim D. February 2014. "Advanced Twig Anatomy: Starting Little to Get Big (Part I)." Arborist News 23(1): 12-18.
Available @ http://viewer.epaperflip.com/Viewer.aspx?docid=957b5dba-214f-475b-b581-a2bb00e328be#?page=12

Gilman, Ed. 2011. An Illustrated Guide to Pruning. Third Edition. Boston MA: Cengage.

Hayes, Ed. 2001. Evaluating Tree Defects. Revised, Special Edition. Rochester MN: Safe Trees.

Marriner, Derdriu. 14 December 2013. “Community and Tree Safety Awareness During Line- and Road-Clearances.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2013/12/community-and-tree-safety-awareness.html

Marriner, Derdriu. 13 October 2013. “Chain-Saw Gear and Tree Work Related Personal Protective Equipment.” Earth and Space News. Sunday.
Available @ https://earth-and-space-news.blogspot.com/2013/10/chain-saw-gear-and-tree-work-related.html

Marriner, Derdriu. 12 October 2013. “Storm Damaged Tree Clearances: Matched Teamwork of People to Equipment.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2013/10/storm-damaged-tree-clearances-matched.html

Marriner, Derdriu. 17 August 2013. “Storm Induced Tree Damage Assessments: Pre-Storm Planned Preparedness.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2013/08/storm-induced-tree-damage-assessments.html

Marriner, Derdriu. 15 June 2013. “Storm Induced Tree Failures From Heavy Tree Weights and Weather Loads.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2013/06/storm-induced-tree-failures-from-heavy.html

Marriner, Derdriu. 13 April 2013. “Urban Tree Root Management Concerns: Defects, Digs, Dirt, Disturbance.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2013/04/urban-tree-root-management-concerns.html

Marriner, Derdriu. 16 February 2013. “Tree Friendly Beneficial Soil Microbes: Inoculations and Occurrences.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2013/02/tree-friendly-beneficial-soil-microbes.html

Marriner, Derdriu. 15 December 2012. “Healthy Urban Tree Root Crown Balances: Soil Properties, Soil Volumes.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2012/12/healthy-urban-tree-root-crown-balances.html

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Available @ https://earth-and-space-news.blogspot.com/2012/10/tree-adaptive-growth-tree-risk.html

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Available @ https://earth-and-space-news.blogspot.com/2012/08/tree-risk-assessment-mitigation-reports.html

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Available @ https://earth-and-space-news.blogspot.com/2012/06/internally-stressed-response-growing.html

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Available @ https://earth-and-space-news.blogspot.com/2012/04/three-tree-risk-assessment-levels.html

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Available @ https://earth-and-space-news.blogspot.com/2012/02/qualitative-tree-risk-assessment-risk.html

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Available @ https://earth-and-space-news.blogspot.com/2012/02/qualitative-tree-risk-assessment.html

Marriner, Derdriu. 10 December 2011. “Tree Risk Assessment: Tree Failures From Defects and From Wind Loads.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2011/12/tree-risk-assessment-tree-failures-from.html

Marriner, Derdriu. 15 October 2011. “Five Tree Felling Plan Steps for Successful Removals and Worker Safety.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2011/10/five-tree-felling-plan-steps-for.html

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Available @ https://earth-and-space-news.blogspot.com/2011/08/natives-and-non-natives-as-successfully.html

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Available @ https://earth-and-space-news.blogspot.com/2011/06/tree-ring-patterns-for-ecosystem-ages.html

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Available @ https://earth-and-space-news.blogspot.com/2011/04/benignly-ugly-tree-disorders-oak-galls.html

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Available @ https://earth-and-space-news.blogspot.com/2011/02/tree-load-can-turn-tree-health-into.html

Marriner, Derdriu. 11 December 2010. “Tree Electrical Safety Knowledge, Precautions, Risks and Standards.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2010/12/tree-electrical-safety-knowledge.html